Sensor format and construction method for capillary-filled diagnostic sensors

ABSTRACT

Sensors for the electro-chemical analysis of samples and methods for the manufacturing of sensors allow for more efficient manufacture and use of electro-chemical sensors. Flexible sheets, such as polycarbonate sheets, are used to easily manufacture sensor components, with sensor chemistry being applied to the sensor components at manufacture. Sensors may be manufactured with modular components, enabling easy production-line manufacture and construction of electro-chemical sensors with significant cost savings and increased efficiency over existing sensor styles and sensor manufacturing techniques.

FIELD OF THE INVENTION

[0001] The present invention relates generally to electro-chemicalanalysis and more specifically to a diagnostic sensor for fluidanalysis.

BACKGROUND OF THE INVENTION

[0002] Electro-chemical analysis is one technique available for theanalysis of both charged and neutral molecules. Such analysis isgenerally very fast, requires small volumes of samples and reagents, andcosts much less than other analysis techniques. Electro-chemicalanalysis can be used for a wide range of applications, including testingof bodily fluids, such as glucose testing of blood samples.Electro-chemical detectors do not require an optical carrier, and as aresult they are much less costly than absorption and fluorescencedetectors. Electro-chemical analysis systems can test samples which arecollected via capillary action within a sensor.

[0003] Generally, most capillary-filled sensors are produced by amethodology wherein active chemical areas are captured within a moldedcapture area. This assembly process requires precision molding, and mayrequire very precise printing of reagents and other chemicals in verysmall areas. Further, the use of a formed molded or laminated structureto define and produce a capillary channel results in a sample beingsubstantially enclosed by formed walls. Irregularities in walls mayfrictionally hinder sample flow and variations of the walls in differentsensors may result in sample fill variations. The resulting sample fillvariations affect the test results and decrease the overall accuracy ofthe analysis. Further, the possibility of trapping air bubbles may beincreased with existing sensors and sensor construction methods. Thereis a need for electro-chemical sensors and sensor construction methodswhich reduce or eliminate these problems to increase the efficiency andaccuracy of electro-chemical sample analysis.

SUMMARY OF THE INVENTION

[0004] According to one embodiment of the present invention, anelectro-chemical sensor consists of a flexible substrate with a chemicalstrip uniformly provided thereon.

[0005] According to another embodiment of the present invention, anelectro-chemical sensor is provided wherein the size and form ofelectrode areas are defined by precision punching. The sample area ofthe electro-chemical sensor is formed by the overlap of twosimilarly-shaped sheets forming a top and bottom, leaving the samplearea open on all sides to form a capillary channel for acquiringsamples.

[0006] According to another embodiment of the present invention, anelectro-chemical sensor is provided wherein the capillary channel isformed by folding an outer sheet over the end of an inner sheet.

[0007] According to yet another embodiment of the present invention, anelectro-chemical sensor is provided wherein the working and referenceelectrodes are produced by the same manufacturing operation.

[0008] According to still another embodiment of the present invention,linear ribbon processing is used to manufacture electrodes and capillaryareas.

[0009] According to still another embodiment of the present invention,electro-chemical sensors are produced in a punch and laminate processusing relatively low-cost, high-speed equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of an electro-chemical sensoraccording to one embodiment of the present invention;

[0011]FIG. 2 is a perspective view of sensor component productionaccording to one embodiment of the present invention;

[0012]FIG. 3 is a side view of an electro-chemical sensor according toone embodiment of the present invention;

[0013]FIG. 4 is an exploded perspective view of an electro-chemicalsensor according to on embodiment of the present invention;

[0014]FIG. 5 is an isometric rear view of an electro-chemical sensoraccording to one embodiment of the present invention;

[0015]FIG. 6 is a perspective view of an electro-chemical sensoraccording to one embodiment of the present invention;

[0016]FIG. 7 is an exploded perspective view of an electro-chemicalsensor according to on embodiment of the present invention;

[0017]FIG. 8 is a perspective view of the assembly of anelectro-chemical sensor according to one embodiment of the presentinvention;

[0018]FIG. 9 is a cross-sectional view of the section defined by line9-9 of FIG. 6; and

[0019]FIG. 10 is a perspective view of an electro-chemical sensoraccording to one embodiment of the present invention connected to ananalysis instrument. While the invention is susceptible to variousmodifications and alternative forms, specific embodiments are shown byway of example in the drawings and will be described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0020] The present invention is generally directed to electro-chemicalsensors and electro-chemical sensor manufacturing methods. Sensorsaccording to the present invention may be used in a variety of settings;one example is use as a glucose testing sensor.

[0021]FIG. 1 shows an electro-chemical sensor 10 according to oneembodiment of the present invention. The electro-chemical sensor 10comprises a top sheet 12, a spacer sheet 14, and a bottom sheet 16.According to one embodiment of the present invention, the sheets used toconstruct the sensor 10 are polycarbonate sheets, but other materialsmay be used in other specific embodiments. According to the embodimentshown in FIG. 1, the top sheet 12 and the bottom sheet 16 of the sensor10 are identically shaped sheets, inverted and overlapped with thespacer sheet 14 placed between them. Adhesive supplied along the top andbottom of the spacer sheet 14 may be used to secure the top sheet 12 andthe bottom sheet 16 to the spacer sheet 14, or other connection meansmay be used as will be appreciated by those skilled in the art.

[0022] The top sheet 12 is provided with a top sheet notch 18 whichaligns with a first spacer sheet notch 20 to expose a bottom sheetelectrode 22. Similarly, the bottom sheet 16 is provided with a bottomsheet notch 24 which aligns with a second spacer sheet notch 26 (bothshown in FIG. 4) to expose a top sheet electrode 28. The electrodes ofthe embodiment shown in FIG. 1 may merely be exposed areas of theconstruction material or a coating material on each of the top sheet 12and the bottom sheet 16, and serve as electrical contacts when thesensor 10 is connected to or inserted into a reading device.

[0023] The electrodes interact with a reading device to allow theanalysis of a sample 30 collected in a sample fill area 32. The samplefill area 32 is between a top sample contact surface 34 and a bottomsample contact surface 36, as shown in FIG. 3. In the embodiment shownin FIG. 1, the top sample contact surface 34 is integrally formed withthe top sheet 12 and is connected to the body of the top sheet 12 by atop neck 38. Similarly, the bottom sample contact surface 36 isintegrally formed with the bottom sheet 16 and is connected to the bodyof the bottom sheet 16 by a bottom neck 40. The overlapping of the topsample contact surface 34 and the bottom sample contact surface 36combined with the gap provided by the spacer sheet 14 causes a fluidsample 30 to be pulled into and remain within the sample fill area 32due to capillary action.

[0024] Turning now to FIG. 2, the construction of sensor sheetsaccording to one embodiment of the present invention is shown. A ribbon42 of construction material is fed into a press 44. According to oneembodiment of the present invention, a coating material 46 is providedon the ribbon 42 before the ribbon enters the press 44. The coatingmaterial 46 may be a surfactant material for increasing the spread of asample as it enters the sample fill area 32, a reagent chemical orcombination of chemicals with which a sample interacts, or a combinationof these.

[0025] The press 44 cuts the ribbon material 42 into a series of stocksheets 48. Each stock sheet 48 may be used as a top sheet 12 or a bottomsheet 16 in the construction of a sensor 10 as shown in FIG. 1. Whetherthe stock sheets 48 are to be used as top sheets or bottom sheets of asensor may be made dependent upon the coating material 46. According toone embodiment of the present invention, the same coating material isprovided on stock sheets 48 to be used as top as on stock sheets to beused as bottom sheets. According to another embodiment, coating materialis provided only on the top sheet or only on the bottom sheet. Further,different coating materials may be used on the two sheets.

[0026] As shown in FIG. 2, the press 44 punches the ribbon material 42such that each stock sheet is provided with a stock sheet notch 50, astock sheet neck 52, and a stock sheet sample contacting surface 54.Thus, in the embodiment shown in FIG. 1, a first stock sheet has beeninverted above a second stock sheet, thereby forming a top sheet 12 anda bottom sheet 16.

[0027] Turning now to FIG. 3, a side view of an electro-chemical sensor10 is shown, illustrating the structure of one embodiment of the samplefill area 32. The sample fill area 32 is located between the top samplecontact surface 34 and the bottom sample contact surface 36, either orboth of which may be coated with coating materials. According to oneembodiment of the present invention, the open space around the samplefill area 32 eliminates the need for an air vent and substantiallyeliminates the trapping of air within the sample fill area 32. Thevolume of the sample fill area 32 is defined by the surface area of thetop and bottom sample contact surfaces 34 and 36 and by the separationdistance, w, shown in FIG. 3. According to one embodiment of the presentinvention, the separation distance w is approximately 0.005 inches,though separations of from approximately 0.003 inches to approximately0.010 inches may be useful in certain embodiments, and wider or narrowerseparations may be useful in some embodiments. The separation distance wmay be adjusted by varying the width of the spacer sheet 14.

[0028] Turning now to FIGS. 4 and 5, an electro-chemical sensor 10 isshown in an exploded view and an a rear view to more clearly illustratethe construction of a sensor according to one embodiment of the presentinvention. As shown in FIG. 4, the spacer sheet 14 is provided withfirst and second spacer sheet notches 20 and 26. In the embodiment shownin FIG. 4, the first spacer sheet notch 20 aligns with a top sheet notch18 and the second spacer sheet notch 26 aligns with a bottom sheet notch24. As a result, when the sensor 10 is formed, the alignment of the topsheet notch 18 and the first spacer sheet notch 20 exposes a bottomsheet electrode 22, as shown in FIG. 1. Likewise, the alignment of thebottom sheet notch 24 and the second spacer sheet notch 26 exposes a topsheet electrode 28, as shown in FIG. 1.

[0029] According to one embodiment of the present invention, the bottomsurface 56 of the top sheet 12 and the top surface 58 of the bottomsheet 16 are coated with conductive material. Thus, electro-chemicalanalysis of the sample 30 can be performed by connecting the exposedelectrodes to an analysis device. According to one embodiment of thepresent invention, carbon coating is used to enable the bottom surface56 of the top sheet and the top surface 58 of the bottom sheet toconduct electricity, though other coatings such may be used in certainembodiments of the present invention. The alignment of the notches inthe top sheet 12, the spacer sheet 14, and bottom sheet 16 is furtherillustrated in FIG. 5, which shows a rear view of a sensor 10 accordingto one embodiment of the present invention.

[0030] Some embodiments of the present invention thus allow for the sizeand form of stock sheets 48 to be defined by precision punching, oranother precise method of production, allowing both a top sheet 12 and abottom sheet 16 to be formed from the same or a very similar process.Further, the application of conductive components, reagents,surfactants, or other chemicals is facilitated by the fact that thecomponents may be applied uniformly over an entire ribbon 42 ofconstruction material or in a single band of coating material 46,reducing or eliminating the need for precision printing or otherprecision placement of coating materials.

[0031] Turning now to FIG. 6, a sensor 60 according to an alternativeembodiment of the present invention is shown. In a sensor 60 accordingto the embodiment shown in FIG. 6, an outer sensor sheet 62 is at leastpartially wrapped around an inner sensor sheet 64. A spacer sheet 66separates the outer sensor sheet 62 from the inner sensor sheet 64 andprovides for a sample fill area 68. According to one embodiment of thesensor 60, the outer sensor sheet 62, the inner sensor sheet 64, and thespacer sheet 66 are comprised of polycarbonate, though other materialssuch as polypropylene may be used in the construction of the sheets.

[0032] An outer electrode area 70 is positioned on the inner surface ofthe outer sensor sheet 62, and an inner electrode area 72 is positionedon a surface of the inner sensor sheet 64. As shown in FIG. 7, the outerelectrode area 70 is provided in a generally “L” shaped layer on theouter sensor sheet 62. Likewise, the inner electrode area 72 is providedin a generally “L” shaped layer on the inner sensor sheet 64. Accordingto the embodiment shown in FIGS. 6 and 7, the spacer sheet 66 is notprovided with an electrode area.

[0033] As shown in FIG. 6, the outer electrode area 70 a singleelectrode coating, functionally divided between an outer electrodesample area 74 and an outer electrode contact area 76. Similarly, theinner electrode area 72 is functionally divided between an innerelectrode sample area 78 and an inner electrode contact area 80. Theelectrode sample areas contact a sample when the sample fill area 68 isfilled with a sample, and conduct electricity to the electrode contactareas, which may be connected to an analysis device to allowelectro-chemical analysis of a sample within the sample fill area 68.

[0034] According to one embodiment of the present invention the outerelectrode area 70 is a reference electrode and the inner electrode area72 is a working electrode. According to another embodiment of thepresent invention, the outer electrode area 70 may be the workingelectrode and the inner electrode area 72 may be the referenceelectrode. The reference electrode may be a printed carbon electrode, oranother type of electrode. The working electrode may be a printed carbonelectrode with a reagent placed thereon. According to one embodiment ofthe present invention, the entire working electrode is a printed carbonelectrode, with reagent placed only on the part of the electrode thatwill contact a sample.

[0035] Turning now to FIG. 8, the construction of a sensor 60 accordingto one embodiment of the present invention is more clearly shown. Thespacer sheet 66 has been placed over a portion of the inner sensor sheet64, leaving the inner electrode sample area 78 exposed. According to oneembodiment of the present invention, the spacer sheet 66 is coated withadhesive on its sheet-contacting sides to enable the finished sensor 60to adhere together. The outer sensor sheet 62 has been placed behind theinner sensor sheet 64. The outer sensor sheet 62 and the inner sensorsheet 64 may be adhered to each other by adhesive placed on the outersensor sheet 62, the inner sensor sheet 64, or both. A distal portion 82of the outer sensor sheet 62 is folded around a portion of the innersensor sheet 64 and the spacer sheet 66 and adhered to the spacer sheet66, thereby forming the sample fill area 68 as shown in FIG. 6.According to some embodiments of the present invention, the sensor 60 isadhered together with adhering methods other than or in addition toadhesives, such as UV cured epoxy.

[0036] Turning now to FIG. 9, a cross-section of the sensor 60 along theline 9-9 of FIG. 6 is shown. A sample 84 has been drawn into the samplefill area 68, for example by capillary action. The sample 84 contactsthe outer electrode sample area 74 and the inner electrode sample area78, enabling electro-chemical analysis of the sample. In the embodimentshown in FIG. 9, the spacer sheet 66 forms one boundary of the samplefill area 68.

[0037] Turning now to FIG. 10, a sensor 60 according to one embodimentof the present invention is shown in use. A sample 84 is being drawninto the sample fill area 68 by capillary action. Further, the sensor 60is connected to an analysis instrument (not shown) by first and secondinstrument contacts 86 and 88. While the sensor 60 is shown being filledwhile connected to the analysis instrument, it is to be understood thatthe sensor 60 may be filled first and connected to an analysisinstrument after filling. The instrument contacts 86 and 88 areconnected, respectively, to the outer electrode contact area 76 and theinner electrode contact area 80. As discussed above, the outer electrodecontact area 76 is in conductive contact with the outer electrode samplearea 74 and the inner electrode contact area 80 is in conductive contactwith the inner electrode sample area 78, thereby enablingelectro-chemical analysis of the sample 84.

[0038] While the present invention has been described with reference toone or more particular embodiments, those skilled in the art willrecognize that many changes may be made thereto without departing fromthe spirit and scope of the present invention. For example, while thepresent invention has been generally described as directed to medicalapplications it is to be understood that any optical fluid testingapplications might employ the principles of the invention. Each of theseembodiments and obvious variations thereof is contemplated as fallingwithin the spirit and scope of the claimed invention, which is set forthin the following claims.

What is claimed is:
 1. A sensor for electro-chemical analysis of asample comprising: a top sheet having a top sample contact surface and atop sheet notch; a bottom sheet having a bottom sample contact surfaceand a bottom sheet notch; and a spacer sheet between said top sheet andsaid bottom sheet and having first and second spacer sheet notches, saidfirst spacer sheet notch aligning with said top sheet notch and saidsecond spacer sheet notch aligning with said bottom sheet notch.
 2. Thesensor of claim 1 wherein said top sheet notch aligns with said firstspacer sheet notch to expose a bottom sheet electrode on a top surfaceof said bottom sheet and said bottom sheet notch aligns with said secondspacer sheet notch to expose a top sheet electrode on a bottom surfaceof said top sheet.
 3. The sensor of claim 1 wherein said top samplecontact surface is positioned above said bottom sample contact surfaceand spaced from said bottom sample contact surface by a separationdistance approximately equal to the width of said spacer sheet.
 4. Thesensor of claim 3 wherein said separation distance is from approximately0.003 inches to approximately 0.010 inches.
 5. The sensor of claim 3wherein said top sample contact surface extends from a body of said topsheet by a top neck and wherein said bottom sample contact surfaceextends from a body of said bottom sheet by a bottom neck, and furtherwherein a volume defined by said top sample contact surface and saidbottom sample contact surface and having a height approximately equal tothe width of said spacer sheet is adapted to contain a sample.
 6. Thesensor of claim 1 wherein said top sample contact surface is coated witha mixture of surfactant and reagent.
 7. The sensor of claim 1 whereinsaid bottom sample contact surface is coated with a mixture ofsurfactant and reagent.
 8. The sensor of claim 1 wherein both said topsample contact surface and said bottom sample contact surface are coatedwith a mixture of sample and reagent.
 9. A method of manufacturing asensor for electro-chemical analysis of a sample comprising: providing aribbon of material; coating a portion of said ribbon of material with achemical mixture; inserting said ribbon of material into a press; andoperating said press to punch a series of stock sheets from said ribbon,said press forming each of said stock sheets having a stock sheet samplecontacting surface substantially uniformly coated with said chemicalmixture; and inverting a first one of said stock sheets over a secondone of said stock sheets to form a sensor.
 10. The method of claim 9wherein said chemical mixture is a reagent.
 11. The method of claim 9wherein said chemical mixture is a surfactant.
 12. The method of claim 9wherein said chemical mixture is a mixture of one or more reagents andsurfactants.
 13. The method of claim 9 further comprising inserting aspacer sheet between said first one of said stock sheets and said secondone of said stock sheets.
 14. The method of claim 9 wherein operatingsaid press to punch a series of stock sheets further comprises punchinga stock sheet notch into each of said stock sheets and furthercomprising inserting a spacer sheet having first and second spacer sheetnotches between said first one of said stock sheets and said second oneof said stock sheets, said first spacer sheet notch aligning with astock sheet notch on said first one of said stock sheets and said secondspacer sheet notch aligning with a stock sheet notch on said second oneof said stock sheets.
 15. A sensor for the electro-chemical analysis ofa sample comprising: an inner sensor sheet having first and secondsides, an inner electrode area provided on at least a portion of saidfirst side; a spacer sheet having first and second sides and connectedalong at least a portion of its first side to a portion of said firstside of said inner sensor sheet; and an outer sensor sheet having anouter electrode area provided thereon and connected to at least aportion of said second side of said inner sensor sheet, a distal portionof said outer sensor sheet being folded around a portion of said innersensor sheet and at least a portion of said spacer sheet and furtherbeing connected to said second side of said spacer sheet, forming asample fill area bounded by a portion of said outer sensor sheet, aportion of said inner sensor sheet, and a portion of said spacer sheet.16. The sensor of claim 15 wherein said inner electrode area comprisesan inner electrode sample area and an inner electrode contact area, saidinner electrode sample area being exposed to said sample fill area. 17.The sensor of claim 16 wherein said spacer sheet is adhesively connectedto a distal portion of said outer sensor sheet and further adhesivelyconnected to a portion of said inner electrode sheet so as to exposesaid inner electrode sample area.
 18. The sensor of claim 15 whereinsaid outer electrode area comprises an outer electrode sample area andan outer electrode contact area, said outer electrode sample area beingexposed to said sample fill area.
 19. The sensor of claim 18 whereinsaid outer electrode sample area is an exposed portion of said outerelectrode area bounded by said spacer sheet and said inner sensor sheet.20. The sensor of claim 15 wherein said inner sensor sheet, said spacersheet, and said outer sensor sheet are comprised of polycarbonate.